504 research outputs found
Surface and vortex structures in noncentrosymmetric superconductors under applied magnetic fields
We investigate how the macroscopic spatial structure of broken inversion
symmetry manifests in noncentrosymmetric superconductors, by the microscopic
broken inversion symmetry of the crystal structure. Based on the time-dependent
Ginzburg-Landau theory including the Pauli paramagnetic effect and the Rashba
interaction, we demonstrate that the centrosymmetric structures of the internal
field and the screening current are broken macroscopically. The flow structure
of paramagnetic supercurrent spontaneously induce the flux flow without
applying external currents.Comment: 5 pages, 8 figures. accepted in Phys. Rev.
Nuclear Magnetic Relaxation Rate in a Noncentrosymmetric Superconductor
For a noncentrosymmetric superconductor such as CePt3Si, we consider a Cooper
pairing model with a two-component order parameter composed of spin-singlet and
spin-triplet pairing components.
We demonstrate that such a model on a qualitative level accounts for
experimentally observed features of the temperature dependence of the nuclear
spin-lattice relaxation rate 1/T1, namely a peak just below Tc and a line-node
gap behavior at low temperatures.Comment: 4 page
Magnetic Properties of a Superconductor with no Inversion Symmetry
We study the magnetic properties of a superconductor in a crystal without symmetry, in particular how the lack of this symmetry exhibits itself.
We show that, though the penetration depth itself shows no such effect, for
suitable orientation of magnetic field, there is a magnetic field discontinuity
at the interface which shows this absence of symmetry. The magnetic field
profile of a vortex in the plane is shown to be identical to that of an
ordinary anisotropic superconductor except for a shift in the direction by
(see errata). For a vortex along , there is an
induced magnetization along the radial direction.Comment: J. Low Temp. Physics, 140, 67 (2005); with Errat
Spin susceptibility in superconductors without inversion symmetry
In materials without spatial inversion symmetry the spin degeneracy of the
conduction electrons can be lifted by an antisymmetric spin-orbit coupling. We
discuss the influence of this spin-orbit coupling on the spin susceptibility of
such superconductors, with a particular emphasis on the recently discovered
heavy Fermion superconductor CePt3Si. We find that, for this compound (with
tetragonal crystal symmetry,) irrespective of the pairing symmetry, the stable
superconducting phases would give a very weak change of the spin susceptibility
for fields along the c-axis and an intermediate reduction for fields in the
basal plane. We also comment on the consequences for the paramagnetic limiting
in this material.Comment: 10 pages, 3 figure
Spectrophotometric properties of dwarf planet Ceres from the VIR spectrometer on board the Dawn mission
We study the spectrophotometric properties of dwarf planet Ceres in the
VIS-IR spectral range by means of hyper-spectral images acquired by the VIR
imaging spectrometer on board the NASA Dawn mission. Disk-resolved observations
with a phase angle within the interval were used
to characterize Ceres' phase curve in the 0.465-4.05 m spectral range.
Hapke's model was applied to perform the photometric correction of the dataset,
allowing us to produce albedo and color maps of the surface. The -band
magnitude phase function of Ceres was fitted with both the classical linear
model and H-G formalism. The single-scattering albedo and the asymmetry
parameter at 0.55m are and ,
respectively (two-lobe Henyey-Greenstein phase function); the modeled geometric
albedo is ; the roughness parameter is
. Albedo maps indicate small variability
on a global scale with an average reflectance of . Isolated
areas such as the Occator bright spots, Haulani, and Oxo show an albedo much
higher than average. We measure a significant spectral phase reddening, and the
average spectral slope of Ceres' surface after photometric correction is
and at VIS and IR wavelengths, respectively.
Broadband color indices are and . H-G
modeling of the -band magnitude phase curve for gives
and , while the classical linear model provides
and . The comparison with
spectrophotometric properties of other minor bodies indicates that Ceres has a
less back-scattering phase function and a slightly higher albedo than comets
and C-type objects. However, the latter represents the closest match in the
usual asteroid taxonomy.Comment: 14 pages, 20 figures, published online on Astronomy and Astrophysics
on 13 February 2017. Revised to reflect minor changes in text and figures
made in proofs, updated value of V-R and R-
Anomalous Spin Response in Non-centrosymmetric Compounds
We examine static spin susceptibilities of spin
components and in the non-centrosymmetric tetragonal
system. These show anomalous momentum dependences like and , which vanish in centrosymmetric systems. The magnitudes of
the anomalous spin susceptibilities are enhanced by the on-site Coulomb
interaction, especially, around an ordering wave vector. The significant and
anomalous momentum dependences of these susceptibilities are explained by a
group theoretical analysis. As the direct probe of the anomalous spin
susceptibility, we propose a polarized neutron scattering experiment.Comment: 4 pages, 1 table, 4 figure
Novel Pressure Phase Diagram of Heavy Fermion Superconductor CePtSi Investigated by ac Calorimetry
The pressure dependences of the antiferromagnetic and superconducting
transition temperatures have been investigated by ac heat capacity measurement
under high pressures for the heavy-fermion superconductor CePtSi without
inversion symmetry in the tetragonal structure. The N\'{e}el temperature
= 2.2 K decreases with increasing pressure and becomes zero at the
critical pressure 0.6 GPa. On the other hand, the
superconducting phase exists in a wider pressure region from ambient pressure
to about 1.5 GPa. The pressure phase diagram of CePtSi is thus very unique
and has never been reported before for other heavy fermion superconductors.Comment: 4 pages and 3 figures. This paper will be published in the July issue
of J. Phys. Soc. Jp
Absence of Aquaporin-4 in Skeletal Muscle Alters Proteins Involved in Bioenergetic Pathways and Calcium Handling
Aquaporin-4 (AQP4) is a water channel expressed at the sarcolemma of fast-twitch skeletal muscle fibers, whose expression is altered in several forms of muscular dystrophies. However, little is known concerning the physiological role of AQP4 in skeletal muscle and its functional and structural interaction with skeletal muscle proteome. Using AQP4-null mice, we analyzed the effect of the absence of AQP4 on the morphology and protein composition of sarcolemma as well as on the whole skeletal muscle proteome. Immunofluorescence analysis showed that the absence of AQP4 did not perturb the expression and cellular localization of the dystrophin-glycoprotein complex proteins, aside from those belonging to the extracellular matrix, and no alteration was found in sarcolemma integrity by dye extravasation assay. With the use of a 2DE-approach (BN/SDS-PAGE), protein maps revealed that in quadriceps, out of 300 Coomassie-blue detected and matched spots, 19 proteins exhibited changed expression in AQP4−/− compared to WT mice. In particular, comparison of the protein profiles revealed 12 up- and 7 down-regulated protein spots in AQP4−/− muscle. Protein identification by MS revealed that the perturbed expression pattern belongs to proteins involved in energy metabolism (i.e. GAPDH, creatine kinase), as well as in Ca2+ handling (i.e. parvalbumin, SERCA1). Western blot analysis, performed on some significantly changed proteins, validated the 2D results. Together these findings suggest AQP4 as a novel determinant in the regulation of skeletal muscle metabolism and better define the role of this water channel in skeletal muscle physiology
Reduction of Pauli paramagnetic pair-breaking effect in antiferromagnetic superconductors
Antiferromagnetic superconductors in a magnetic field are studied. We examine
a mechanism which significantly reduces the Pauli paramagnetic pair-breaking
effect. The mechanism is realized even in the presence of the orbital
pair-breaking effect. We illustrate it using a three-dimensional model with an
intercalated magnetic subsystem. The upper critical field is calculated for
various parameters. It is shown that the upper critical field can reach several
times the pure Pauli paramagnetic limit. The possible relevance to the large
upper critical field observed in the heavy fermion antiferromagnetic
superconductor CePt_3Si discovered recently is briefly discussed. We try to
understand the large upper critical field in the compound CePt_3Si and
field-induced superconductivity in the compound CePb_3 within a unified
framework.Comment: 5 pages, 2 figures, revtex4, minor correction
Emergent Nodal Excitations due to the Coexistence of Superconductivity and Antiferromagnetism: Cases with and without Inversion Symmetry
We argue the emergence of nodal excitations due to the coupling with static
antiferromagnetic order in fully-gapped superconducting states in both cases
with and without inversion symmetry. This line node structure is not
accompanied with the sign change of the superconducting gap, in contrast to
usual unconventional Cooper pairs with higher angular momenta. In the case
without inversion symmetry, the stability of the nodal excitations crucially
depends on the direction of the antiferromagnetic staggered magnetic moment. A
possible realization of this phenomenon in CePtSi is discussed.Comment: 4 pages, 7 figure
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